A previous Premarin/Medroxyprogesterone (MPA) Acetate study evaluated a daily dose of Premarin 0.625mg combined with various doses of MPA in both continuous combined and cyclic regimens. Following the successful completion of that study it was thought to be appropriate to explore the safety and efficacy of lower doses of Premarin/MPA in continuous combined regimens to determine if the addition of MPA would allow the use of a daily dose of Premarin less than 0.625mg daily which would be effective in preventing bone loss, relieving vasomotor symptoms and maintaining acceptable bleeding and metabolic profiles. The primary endpoints are prevention of endometrial hyperplasia during the first year of the study and prevention of bone loss. It is a prospective double-blind, randomized study. Fischer's exact test will be used for comparison between groups for the incidence of hyperplasia.